The present invention relates to new and useful oxazolidinone compounds and their preparations, and more particularly to oxazolidinone compounds in which the carbonyl functionality of --NH--C(O)--R is converted to a thiocarbonyl functionality, such as a thiourea --NH--C(S)--NH.sub.2, an alkyl thiourea --NH--C(S)--NH--(C.sub.1-4 alkyl), thioamide --NH--C(S)--(C.sub.1-4 alkyl) or --NH--C(S)--H.
Replacement of the oxygen atom with a sulfur atom has unexpectedly improved the antimicrobial properties of the compounds. The compounds are useful antimicrobial agents, effective against a number of human and veterinary pathogens, including Gram-positive aerobic bacteria such as multiply-resistant staphylococci and streptococci, Gram-negative organisms such as H. influenzae and M. catarrahlis as well as anaerobic organisms such as bacteroides and clostridia species, and acid-fast organisms such as Mycobacterium tuberculosis and Mycobacterium avium. The compounds are particularly useful because they are effective against the latter organisms which are known to be responsible for infection in persons with AIDS.